Abstract : The present study was a further investigation of the trainability of target classification skills; but differed from the earlier studies in several important respects: (a) the experimental training course was longer (19 hours); (b) the various training sessions were distributed throughout several weeks of general operator training at the Fleet ASW School; (c) better training materials were available; (d) a more systematic approach to target classification was used; and (e) the perceptual and conceptual responses of the students, the necessary prerequisites to correct classification, were recorded. Diagnosis of the reasons for target classification failures was attempted. The answers have implications not only for future training practices but also for the design of sonar systems that incorporate classification computers. Since the difference in scores between the groups was statistically significant, and since only the experimental group's score deviated significantly from that expected by chance, it may be concluded that there was a significant training effect. As with previous studies of classification training, however, the level of perfor ance, even for the difficult targets in the test, left much to be desired. (Author)